Theophylline is a prescription drug with a long history as a treatment for asthma (a chronic inflammation of the airway tissues). As one of the first long-term bronchodilators (medications that widen the airways by relaxing the smooth muscle), it has also been used to treat other respiratory disorders such as bronchitis, emphysema and chronic obstructive pulmonary disease (COPD). In recent years, the medication had fallen out of favor with some physicians because of concerns about the danger of toxicity from having too much of the drug in the bloodstream.

However, new discoveries about the medication's effects on inflammation and immune function related to asthma have renewed interest in theophylline. It may be a useful drug to combine with low-dose inhaled corticosteroids (medications that prevent the inflammation associated with asthma attacks) for asthma management. There also is evidence that the drug has a more powerful anti-inflammatory effect than high-dose inhaled corticosteroids in treating COPD. In addition, new extended-release forms of the medication have made it somewhat easier to ensure that patients have just the right amount of theophylline in their bloodstream at all times.

Despite these improvements, theophylline is a drug that must be used with caution. Illnesses, smoking and other medications can alter the rate at which the drug is cleared from the body. Patients who take theophylline must have their blood checked regularly to ensure that the concentration of the medication in their bloodstream remains at a therapeutic level – enough to be effective, but not so much that it becomes toxic.